When using a tool with a robotic hand-arm system, the stiffness at the grasped object plays a key role in the interaction with the environment, allowing the successful execution of the task. However, the rapidly increasing use of under-actuated hands in robotic systems due to their robustness and simplicity of control, pose limitations to the achievable object-level stiffness. Indeed, due to the serial coupling of the hand and the arm, the resulting object-level stiffness is determined by the most compliant of both elements. To address this problem, we propose a novel controller that takes into account the limited achievable geometry of the object stiffness ellipsoid given by a hand with under-actuation constraints, and exploits the contribution of the robotic arm in reshaping the final stiffness towards the desired profile. The under-actuation is illustrated by a coordinated stiffening of the hand fingers. The proposed method is experimentally validated by a hand-arm system performing a peg-in-hole task.

当使用带有机械手系统的工具时，所抓取物体的刚度在与环境的交互中起关键作用，从而可以成功执行任务。然而，由于机器人系统的鲁棒性和控制的简单性，在机械系统中使用不足的手的迅速增加对可达到的物体水平的刚度造成了限制。实际上，由于手和手臂的串联耦合，最终产生的对象级刚度由两个元素的最顺应性确定。为了解决这个问题，我们提出了一种新颖的控制器，该控制器考虑了具有欠驱动约束的手给定的物体刚度椭球的有限可实现几何形状，并利用了机械臂在将最终刚度重塑为所需轮廓方面的贡献。欠驱动通过手指的协调刚度来说明。提出的方法通过执行钉孔任务的手臂系统进行了实验验证。